In a wireless communications system many types of traffic are present. One type of traffic sent over a wireless communications system is data. Data is bursty by nature. Examples of data sent over a wireless communications system are e-mail messages and text messages. Delay sensitive traffic is a more common form of data sent over a wireless communications system. Voice communications is an example of delay sensitive traffic. The difference between voice and data is that voice is a real time application that has minimal tolerance for conditions such as delay, and more tolerance for packet loss. In a communications system, voice is packetized. In other words, the conversation is digitized and encapsulated into a packet. These packets are transported across networks and transmitted to mobile stations.
Scheduling is employed to manage delay sensitive traffic in a time-shared wireless communications system. For delay sensitive traffic, the end-to-end delay should be within a certain bound to satisfy quality criteria dictated by quality of service requirements.
As a general rule in wireless communications systems, packets with a queuing delay at a transmitting station that exceeds a pre-determined amount of time are discarded. As a result, packet loss occurs, which eventually gives rise to user outage or, at the very least, reduced and/or unacceptable quality.
The current scheduling systems are often unable to maintain the necessary quality of service needed to prevent gaps in conversations. Latency is the average time it takes for a packet to reach a destination from the source. The typical amount of latency for a voice call is 100 milliseconds. Packet loss occurs when packets are dropped by the wireless communications system when too much latency is present for a packet. In the case of dropped voice packets, the packets are discarded and not retransmitted. Typically, voice traffic can tolerate up to a three percent loss of packets before callers experience disconcerting gaps in conversation. A one percent drop or less in voice packets is optimal.
Therefore, it would be advantageous to have an improved method, apparatus, and computer usable program code for scheduling the transmission of delay sensitive traffic to a mobile station.